Silicon carbide (SiC) is now in developments as a next-stage material for a power device. As compared to silicon (Si) conventionally used as a semiconductor material, the SiC has characteristics of a high band gap, a high breakdown field (10 times as high as that of the Si), and a high thermal conductivity. The SiC also has high thermochemical stability.
Making transistors using the SiC may require doping impurities into the SiC. Conventionally, doping impurities into the Si may be performed by irradiating the Si with an ion beam of the impurities, and then applying a high temperature to activate the impurities. However, using such a conventional process on the SiC may result in a thermal damage on the SiC to form a lattice defect, degrading electrical characteristics of the SiC.
Non-patent Documents 1 to 5 listed below discuss laser doping in which the SiC is irradiated in dopant-containing solution with a pulse laser beam. However, sufficient doping depth may not be achieved in Non-patent Documents 1 to 5 as described below:
(1) Regarding an n-type dopant, doping depth of nitrogen (N) in a range of 100 nm to 200 nm is reported. However, doping depth of phosphor (P) is only around 30 nm.
(2) Regarding a p-type dopant, doping depth of aluminum (Al) of approximately 40 nm is reported. However, greater doping depth than that is not reported.
Non-patent Document 1: Akihiro Ikeda, Koji Nishi, Hiroshi Ikenoue, Tanemasa Asano, Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation, APPLIED PHYSICS LETTERS 102, 052104 (2013)
Non-patent Document 2: Koji Nishi, Akihiro Ikeda, Hiroshi Ikenoue, and Tanemasa Asano, Phosphorus doping into 4H-SiC by Irradiation of Excimer Laser in Phosphoric Solution, Japanese Journal of Applied Physics 52 (2013)
Non-patent Document 3: Daichi Marui, Akihiro Ikeda, Koji Nishi, Hiroshi Ikenoue, Tanemasa Asano, Aluminum doping of 4H-SiC by irradiation of excimer laser in aluminum chloride solution, Japanese Journal of Applied Physics 53 (2014)
Non-patent Document 4: Akihiro Ikeda, Daichi Marui, Hiroshi Ikenoue, Tanemasa Asano, Nitrogen doping of 4H-SiC by KrF excimer laser irradiation in liquid nitrogen, Japanese Journal of Applied Physics 54(2015)
Non-patent Document 5: Yuuki Inoue, Hiroshi Ikenoue, Akihiro Ikeda, Daisuke Nakamura, Tatsuo Okada, Tanemasa Asano, N-type Doping in 4H-SiC by Laser Irradiation in Chemical Solutions and its Diffusion Properties of Impurities, The 61st Japan Society of Applied Physics Spring Meeting (2014)
Patent Document 1: Japanese Patent No. 4387091
Patent Document 2: Japanese Patent No. 4409231
Patent Document 3: Japanese Patent Application Publication No. 2010-525554
Patent Document 4: International Publication No. WO 2014/156818